Electric-motor starter



April l, 1930. w. T. HOLMES ELECTRIC MOTOR STARTER Filed Jan. 7, 1928 LYM /IL J, ff

ATTORNEY.

'n the armature current.

' dated Patented Apr. 1, 1930 WILLIAM T. HOLMES, or

SAID WILLIAM T. HOLMES, DECEASED, ASSIGNOR TO BALTIMORE, MARYLAND; DAISYN. HOLMES, EXEGUTRIX OF MONITOR CONTROLLER GOM- LPANY, OF BALTIMORE,MARYLAND, A CORPORATION OF MARYLAND ELECTRIC-MOTOR STARTER 1 Applicationed January 7, 1928. Serial No. 245,156.

rhis invention relates to electric motor starters of the class whereinthe cutting out of the starting resistance is controlled by current iiowin the armature circuit of the motor. In the patent to IVhittingham, No.1,135,870, pril 13, 1915, is shown a starter in which a centrallypivoted contactor is rocked to closing position by a magnet having itscoils connected across the line in a circuit independent of the armaturecircuit of the motor, and a magnet, having its coils in series with thearmature circuit, acts in opposition to the first mentioned magnet andprevents the closure of the contactor until the armature current fallsto a predetermined value. This starter operates satisfactorily under allwerking conditions; but under very unusual conditions, as may be broughtabout by temporary grounds or short circuits on the supply circuit, thevoltage at the terminals of the magnet which rocks the contactor toclosed position, may be lowered to such an extent that it will notoverpower the series magnet and close the contactor when the current inthe coils of the series magnet is at the predetermined value where,under ordinary conditions, the contactor would close. In the presentinvention, the main and auxiliary contactors are moved to their closedpositions and held in such positions by magnets, the coils of which areconnected across the line, but they are not acted upon or retarded byseries coils, as in the patent referred to, and therefore will be heldin their closed positions even witha very large drop in line voltage.The timing of the closure of the auxiliary contactors, in the presentinvention, is attained by the use of relays, each having a magnetconnected in shunt to a part of the starting resistance, whereby therelay is controlled by Each relay controls the circuit of a. magnet forclosing an auxiliary contactor and operates to close said circuitwhenthe armature current falls to a predetermined value. By thisarrangement, the time of closure of the auxiliary contactors iscontrolled by the armature current, but there is no magnetic forceapplied to the contactors tending to open the same, and hence themagnets which close the contactors will hold them cuit through theresistance, and auxiliary con- A tactors b and c, for cutting out theresistance.

These contactors are adapted to be closed by magnets l, 2, and 3, whichmagnets are mounted upon metalbases 122% ant 3a, respectively. rIhestarting resistance is connected to the bases of the magnets, as shown,thus dividing if he resistance into sections r and 1. The armaturecircuit extends from the starting resistance by conductor 4 to thearmature m, and thence to the supply wire L. The field 7 ofthe motor isconnected to the supply wire L, and also by conductor 5 to the base 1aof the magnet 1. rI'he contactors a, Z), and 0 are adapted to engagestationary contacts 6, 7, and 8, respectively, which contacts areconnected by conductor 9 to the supply wire L, as i shown. T hecontactors are pivotrally mounted upon the magnet bases, as shown, andare therefore electrically connected to said bases.

It will be seen that when the contactor a closes against the Contact 6,current will flow from the supply wire L, through the contactor fr andthe base la to the field of the motor through the conductor 5, and alsoto the armature of the motor through the entire resistance It. When theauxiliary contactor Z2 closes, current will flow from the stationarycontact 7 through contactor b and magnet base 2a to the section r of thestarting resistance, and v thence to the motor, thus short circuitingthe section r of the starting resistance. When the contactor c closes,current will flow through stationary contact 8 and this contactorthroughbase 3 directly to the motor, thus short circuiting the section r of theresistance.

The coils of the magnets l, 2and 3, when in circuit, are connectedacross the line and receive the .tull line voltage. ,The `circuit ot'the magnet 1 is controlled by a hand switch L, so that immediately uponclosure oi? the switch the contactor a will close; but the circuits oitthe magnets 2 and 3 of the auxiliary contactors are controlled by relaysZ and CZ',

so that said contactors close in succession at predetern'iined currentvalues in the armature circuit ot' the motor.

The circuits ot the relay magnets 10 and 11 are connected in shunt toportions of the starting resistance. The relay Z comprises the magnet10, mounted upon a suitable base 10, connected to the base 1, and anarmature 1.2, which is constantly urged away from the magnet. by aspring 13. rthis armature is adapted to engage a stationary con-tact 14,but is normally `held out of engagement with said contact and in closerelation to the pole of the .magnet 10 by an extension a on the maincontacter fr. The relay d is similar to the rel-ay d, and its armature15 is adapted to engage a stationary Contact 16,` but. is normally heldout of engagement with said contact :by an extension 7) on the auxiliarycontacter Thelbase 11a of the relay magnet 11 is `electrically connectedto the base 2"L yot the magnet 2.

The switch blade 18 ot the switch .72, is connected by conductor 19 tothe supply wire L, and this bla de is adapted to engage stationarycontacts 2O and 21 practicall i at the same time. A conductor 22connects the contacts 21 with the coils of the shunt magnet- 1, andthese coils are connected by conductor 23 to 'the supply wire L. Hence,when the switch -k is closed, the magnet 1 will be energized and themain contacter will engage the stationary contact 6 `and close 'thearmature circuit through the entire resistance. A conductor 24 connectsthe contact 20 with the coil of the relay magnet 10, and a conductor .25extends from this *coil to an adjustable contact member 26, whichengages the resistance section Hence, when the switch L closes, themagnet of 'the relay Z will be strongly .energized by current flowingthrough the circuit just traced to the resistance and thence to themotor. The contactor a, in closing, releases the armature 12; but thecurrent flowing through the magnet 10 holds the armature 12 away fromthe contact 14 until the current 1n the coil of the magnet 1'0 falls toa predetermined value, when the magnet releases the armature and thelatter is moved by the spring 13 into engagement with the contact 14.

It is to be noted that when the switch 7L is closed, the magnety coilsof 'the relay Z are connected in shunt to that portion of the "startingresistance which is included between the base V1a the point where theadjustable arm 26 engages the resistance. Hence, the 'armature currentwill divide between said portion of the resistance and the coil of themagnet 10, and the latter will hold the armature 12 until the current inthe armature circuit o the motor falls to a predetermined degree, whenthe armature 12 will move away from the magnet 10 and engage the contact14. The time of release of the armature 12 by the magnet may be variedby adjustment of the spring 13 or adjustment of the arm 26 to includemore or less ot' the starting resistance in parallel with the coils ofthe relay magnet.

When the armature of the relay cl engages the contact 14, it closes acircuit through the shunt magnet 2 of the auxiliary contactor b, andalso a circuit through the coil of the magnet 11 of the relay CZ. Thus,the contact 14 is connected by conducto-r 27 to the coil of the magnet2, and thence by conductors 28 and 23 to .the supply wire L. The circuitof the magnet 11 of relay d extends from the Acontact v14., throughyconductor 27 to conductor 29, thence through the magnet coil and byconductor 30 to the adjustable arm 31 which engages the section r of thestarting .resistance. It will be seen that when the relay armature 12engages the contact 14, current will flow through the main lcontacter ato the vbase 10L of the relay CZ, thence through armature 12 to thecontact .14, from whence current will flow through the coils of mag-Vnet 2 and through the coils of the magnet 11 of rela-yd. The auxiliarycontactor Z) will be immediately mov-ed to the closed position by themagnet 2, and the extension o of the contacter will be moved away fromthe armature 15 of the relay. The main contactor will cut -out thesection r of the starting resistance, and the coils `of the relay magnetwill remain .in parallel with la part of the section r of the startingresistance. When the armature current tal-ls to a predetermined value,the relay al will release its armature 15 and the .latter willengage thecontact .16, thereby closing the circuit through the magnet 3, whichcontrols ythe auxiliary contactor 0. This circuit extends .from 'thecontactor b, through the base 11a of the relay to the armature 15,thence to contact 16, thence through conductor 32Vto the 'coils ot'magnet 3, and thence through conductors l33 and `23 to the side L of thesupply circuit. Upon the closure of this mag-net circuit the contactor 0will instantly close and short circuit the section r of the 'startingresistance. l

From the foregoing, .it will seen that upon closure of the manuallyoperable switch It, the main contactor a will close instantly, but `thetime of closure of the auxiliary contactors will be determined by thevolume of current in the armature circ-uit. The .shunt connected magnets1, 2, and 3, which close the contactors, may be made of Vsuch strengththat they will hold the contactors closed even with a very considerabledrop .in voltage, as may occur with grounds .and short circuits on theline, er from other causes. Thus, in the starter described, the cuttingout of the starting resistance is controlled bythe current in thearmature circuit, but the contactors are held in their closed positionsby magnets which are not affected by fluctuations el' the `armaturecurrent, and hence they will stay closed under all Working conditions ofthe motor and will be released only when there is a very heavy drop involtage en the line, or when the switch h is opened to stop the motor.

Then the switch L is opened, it will interrupt the circuit of the magnetl and the latter will release the main contacter, and it will also openthe circuit through the relay magnet 10, and current will thus be cuteil' from the meter. The main contacter, in opening, Will move the relayarmature l2 away from the contact 14 and into close relation to themagnet l0, thus interrupting the circuit through the magnet 2 of theauxiliary contacter Z), and also through the relay magnet 1l. Thecentactert will move the relay armature 15 out of engagement withcontact 16, thus interrupting the circuit through the magnet 3 or'contacter c, and the latter will tall back to its normal position.

In Fig. 2 of the drawing, I have shoxvna modified ferm et starter,comprising a main contacter and an auxiliary contacter, in which theswitch arm of the current-centrelled relay is not held in normalposition mechanically by a contacter.

-eterring to Fig". 2, S indicates the starter and lvl indicates a motorcontrolled by the starter. A main contacter 0,2 is adapted to be closedby a shunt magnet 35, and the auriiliary contacter c2 is adapted to beclosed by a shunt magnet 36. A relay (Z2 controls the circuit et' themagnet 36. lThe starting resistane is connected te the bases and 36 etthe magnets and 38, respectively, and the field circuit 37 et the meteris connected te the base 35 and to the supply wire li', as shown. Thecontactors a2 and 02 are adapted te engage fixed contacts 3S and 39,respectively, which latter' are connected by a Wire 40 to the supplyWire L. A conductor 4l leads from the supply Wire L to a relay Contact42, vwhich is adapted te be engaged by the relay armature 43, but thelatter is normally held out of engagement with said Contact by anadjustable spring 44. A circuit extends trom conductor 41, through anormally open push button switch l), by Way et conductors 43 and 44 tothe coils or" relay magnet 45, and thence by conductor 46 to adjustablecontact I?, which engages the resistance section r at a pointintermediate the bases 35a and It `vill be evident that when the pushbuttm switch P is closed, current will new Jfrom th supply Wire Lthrough the circuit just cf te the resistance r3, and thence throughmeter armature m te the supply Wire L', and

the magnet Will be energized. This magnet will move the switch arm 43out of engagement With a contact 48 and into engagement with the contact42.` l/Vhen the switch arm 43 engages contact-42, a circuit Will becompleted through the magnet 35 et the main contacter as follows: 'fromsupply Wire L, through conductor 4l te switch arm 43, thence through thebase 49 et' the relay magnet to conductor o0, thencethrough conducter 5lto a normally closed stop push button switch 52, thence throughconductor 53 t0 the coils el magnet 35, thence 'through conductor te theside la el the supply circuit. The magnet 35 Will cause the maincontacter te close, and .when sai-d contacter closes, it

will complete the motor circuits and alsoy complete holding circuitsthreu 'h the magnets 45 and 35, so that these magnets will remainenergized after the operator releases the push button switch l). Thus,When the main contacter closes, it connects the side L oi the supplycirc it to contact 55, which is connected by conductor 5G to conductor44, and hence current 'from the supply Wire la can 'flow through thecontacter and conductor 44 to the relay magnet 45 alter the start pushbutton l? has been released, and the relay magnet will hold the switcharm 43 in engagement vith contact 42. The main contacter will alsoconnect a contact 57 with the supply Wire L, an-d current will llevvfrom said contact throughconductors 58 and 5l to the stop push buttonswitch 52, thence through the shunt magnet 35 to theA supply wire L. Themagnet 35 will therefore be energized even vai'ter the relay magnet 4oreleases the switch arm 43.

By reason et the circuits thus traced, the closure o'li the start pushbutton switch Will cause the relay switch te close a circuit through themagnet oi the main contacter, and the latter' Will immediately close themotor circuits and the magnet of the coils et the relay switchvvill beincluded in shunt to that portion et the starting resistance which liesbetween the bases 35a and the adjustable contact `member 4?. l/Vhen thecurrent in the armature circuit falls to a predetermined value, therelay magnet releases the switch arm 43, Which is then drawn by thespring-44 into engagement With the contact 43. This completes a circuitthrough the shunt magnet36 or" the auxiliary contact-or c2 as follows:from the supply Wire'L.v through main contacter andcenducters 58 and tothe base 49 of the relay, thence through switch arm 43 and contact 48 toconductor 59, thence through coils et magnet 36 and by conductors 60 and54 to the supply ivire L. The magnet 36 Will cause the contactor c2 toclose, thus cutting out the starting resistance and at the same timeclosing ay holding circuit through the magnet 36. This latter circuitextends from a contact 61,

which the main contacter engages, through conductor 62 to. the wire 59,thence through coils of magnet 36 and by conductors 60 and 54; to thesupply wire L.

It will be evident that in the starter of F ig. 2, the time of closureof the auxiliary contacter, which cuts out the starting rcsistance, iscontrolled by the armature current, which divides between the relaymagnet and a part of the starting resistance. lt will also be evidentthat when the circuits of the magnets 35 and 36 are made up thecontactors will immediately close. These magnets may be Wound so as toretain the contactors in their closed positions, notwithstanding widechanges in the line voltage, and it will be evident that the magnets arenot affected by fluctuations in armature current.

To stop the motor, it is merely necessary to open the stop push buttonswitch 52, which interrupts the circuit through the main contactormagnet and its contacter, in opening, opens the circuit through therelay magnet and the circuit which extends through the base of saidmagnet to the magnet 36 of the auxiliary contractor. lence, upon openingthe stop push button switch. the parts will move to the position shownin the drawing.

lhat I claim is:

l. The combination with a supply circuit, of a motor starter comprisinga starting resistance, main and auxiliary contactors, magnets forclosing the contactors, said magnets having circuits independent of thearmature circuit of the motor, a relay comprising a switch memberadapted to close the circuit of the magnet of the auxiliary contacterand a magnet having windings in parallel with part of the resistance forcontrolling the movement of said member, said main centactor adapted tonormally hold said member close to the relay magnet and to release saidmember and connect the same to the supply circuit when said maincontacter closes.

2. The combination with a supply circuit, ot' a motor starter comprisinga starting resist-ance, main and auxiliary contactors, magnets forclosing the contactors, said magnets having circuits independent of thearmature circuit of' the motor, a relay comprising a magnet havingwindings in parallel with part of the resistance and an armaturenermal'ly held in close relation to the relay magnet by said maincontactor, said main contactor, in closing, adapted to release saidarmature, and the latter adapted to close the circuit of the magnet ofthe vauxiliary contactor when released by the relay magnet.

3*. The combinati-on with a supply circuit, of a motor startercomprising a starting resistance, a ser-ies of contactors, magnets forclosing the contactors, said magnets having circuits independent of thearmature circuit of the motor, relays associated withV the severalcontactors in the series except the last vIiP/53,116

one, each relay comprising a magnet having windings in parallel withpartof the start ing resistance and an armature normally held in closerelation to the relay magnet by the Vcontactor with which it isassociated and adapted to be released when the contacter closes, and thearmature of eaca relay adapt@ ed to close the circuit of the magnet ofthe next contactor in the series when released by the relay magnet.

il. The combination with a supply circuit, of a motor startercon'iprising a starting resistance, a series of contactors, magnets forclosing the contactors, said magnets having circuits independent of thearmature circuit olf the motor, relays asseciated with the seycralcontactors in the series except the last one, each relay comprising amagnet having windings in parallel with part of the starting resistanceand an armature normally held in close relation to the relay magnet bythe contacterv with which it is associated and adapted to be releasedwhen the contactor closes, andthe armature of the relay associated withthe first contactor in the series adapted to close the circuit of themagnet ot' the next contactor in the series and also to close thecircuit of the relay magnet associated with the latter contactor. v

5. The combination with a supply circuit, ct a motor starter comprisinga starting resistance, main and auxiliary contactors, magnets torclosing the'contactors, said magnets having circuits independent of thearmature circuit of the motor, a relay comprising a switch membernormally tending to close the circuit of the magnet of the auxiliarycontactor and a magnet having windings in parallel with part only of theresistance for controlling the movement of said member, said maincontact-or adapted to normally bear against and hold said member in openpostion and to release said member and connect the same to the supplycircuit when said main contacter closes.

In testimony whereof I hereunto alix my signature. l

VILLIAM T. HOLMES.

